This invention relates to air conditioning and ventilation systems in general, and specifically to a means for improving the efficiency of front end mounted heat exchangers.
Liquid cooled, internal combustion automotive engines are typically mounted at the front of the vehicle, in an engine compartment located behind a grilled front end air opening in the vehicle body. Outside air is naturally forced rearwardly through the front end opening as the vehicle moves forward at speed, generally referred to as ram air. Engine cooling is provided by a radiator mounted behind the grill, which liquid coolant continually pumped through it, and ram air flowing over it. The radiator also requires a cooling fan to blow air over it at low or zero vehicle speeds. Such fans are typically mounted just behind the radiator and run in only one direction, so as to pull air rearwardly through the radiator, as there would generally be no need to provide a reverse air flow.
The ready supply of heated engine coolant being pumped continually through the radiator and engine is conventionally tapped for passenger space heating in cold temperatures. Liquid engine coolant is diverted through what is, in effect, a miniature radiator, known as a heater core. Air forced over the heater core from yet another fan picks up heat for vehicle passenger space heating. As the vehicle first starts out on a cold day, when the engine has not yet warmed up, the forced air flow through the radiator is an impediment to fast heater core warm up. A wide variety of devices have been proposed over the years, from simple covers fastened over the outside of the grill, to moveable vane assemblies, to block the front end air opening temporarily, and speed the warm up process.
Apart from the long felt problem of cold day heater warm up delay, a new challenge in passenger space heating has arisen. As liquid cooled, automotive vehicle engines become smaller and more efficient, they inevitably produce less waste heat. While this eases the need for power train cooling, it is a real problem for the typical, diverted coolant passenger space heating unit. One proposed solution is to use a heat pump system which, theoretically, extracts heat from the outside air, even from cold outside air. Such systems may be used in place of, or as a supplement to, conventional engine coolant diversion systems. Air conditioning or cooling systems mount a condenser in front of and parallel to the radiator, so that outside air, either ram, fan blown, or both, passes through the two heat exchangers in series. Pressurized refrigerant pumped through the condenser, primarily in hot weather, gives up heat to the passing outside air before it reaches the radiator. By making the cooling system reversible (heat pump), the condenser can also be used in reverse in the winter, to pick up heat from the passing outside air before it reaches the radiator. In such case, the condenser is generally referred to as just the xe2x80x9coutsidexe2x80x9d heat exchanger, since it may serve under high pressure (summer) or low pressure (winter) alternately. A long felt problem with a heat pump system used for supplementary heating is that its efficiency is least just when it is most needed, that is, in cold winter weather. Not only does the outside air have less heat energy to give up, but icing of the outside heat exchanger may occur, blocking air flow to the engine cooling radiator behind. A typical de-icing protocol for a heat pump involves running it in summer mode (the reverse of reverse, in effect), which does melt the ice, but which has the decidedly unwelcome side effect of cooling the passenger space.
The invention provides a novel mechanism for incorporation with the front air opening, radiator, radiator fan and/or outside heat exchanger as defined above, which has the potential to solve all of the problems outlined above, including rapid warm up, lack of cold weather heat pump efficiency, and cold weather outside heat exchanger icing.
In the preferred embodiment disclosed, a flexible film panel is adapted to roll back and forth in a general L shape, with a first, vertical length in front of the condenser/outside heat exchanger, just behind the grill, and a horizontal length running below the heat exchangers and fan. A window in the panel can be selectively located in the horizontal or vertical position, covering or uncovering the front end opening, and thus blocking or un blocking the flow or forced air therethrough. In addition, a means is provided to reverse the radiator cooling fan, most conveniently a reversible electric drive motor.
When a quick warm up is desired, the flexible panel is rolled to the second position, which locates the window in the horizontal position. This leaves the front end covered and substantially blocks the normal, rearward ram air flow through the radiator, and also through the condenser/outside heat exchanger, if one is present. This alone creates a quicker warm up of the engine and conventional liquid engine coolant fed heater core. If desired, the radiator coolant fan can be concurrently run in reverse, establishing a forward moving cooling flow of air through the radiator, unencumbered by the now blocked, normal rearward ram air flow. Such air would be drawn from and through the engine compartment, potentially helping to warm up the radiator even more quickly. This forward, fan air flow would impact the film panel, and then exit the window, which is located below.
In addition, when a condenser/outside heat exchanger is mounted in front of the radiator (but still behind the film panel), ram air flow through it will be blocked, as well. If the fan is also run in reverse, air from the engine compartment will run forwardly through the radiator, pick up heat therefrom, and then flow through the outside heat exchanger. Such air is generally significantly warmer than the blocked outside ram air flow, especially so under the very cold conditions when an accelerated warm up would be required. When the cooling system is being used as a heat pump, its efficiency is thereby enhanced, since it is extracting heat from a warmer air flow. The potential for icing up is also reduced significantly.
Conventional operation is achieved simply by rolling the panel window up to the first position, which leaves the front end air opening un blocked. In addition, the potential exists to only partially block the front end opening, while blocking the area beneath the radiator and condenser with the horizontal length of the flexible panel. This improves operation at idle by allowing the fan to pull enough outside air in to cool the radiator, while the heated air that has flowed rearwardly through the condenser is prevented from recirculating back up and through the front end air stream.